Probe driving method, and probe apparatus

ABSTRACT

A probe driving method and a probe apparatus for bringing a probe into contact with the surface of a sample in a safe and efficient manner by monitoring the probe height. Information about the height of the probe from the sample surface is obtained by detecting a probe shadow ( 54 ) appearing immediately before the probe contacts the sample, or based on a change in relative positions of a probe image and a sample image that are formed as an ion beam is irradiated diagonally.

The present application is a continuation of application Ser. No.10/296,887, filed Nov. 29, 2002, the contents of which are incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to probe apparatuses for bringing amechanical probe into contact with the surface of a sample. For example,the invention relates to a sample preparing apparatus for preparing amicroscopic device or a sample section for microscopic region analysisby separating and removing, by means of an ion beam and a probe, amicroscopic sample section comprising a specific region of a samplesubstrate. The invention also relates to a sample diagnostic apparatusfor measuring the characteristics of a sample by e.g., applying avoltage to the surface of the sample with a probe.

BACKGROUND OF THE INVENTION

JP Patent Publication (Unexamined Application) No. 5-52721: “Method ofseparating a sample and a method of analyzing a separated sampleobtained by the separating method” (Publication 1) discloses a method ofpreparing a sample by separating and removing a microscopic samplesection of the micrometer order with a mechanical probe. In thispublication, a change in probe potential caused by the contacting of aprobe to the substrate is captured as a change in luminance in ascanning ion microscopy image (to be hereafter referred to as SIMimage), to judge the contact of the probe to the substrate surface.

JP Patent Publication (Unexamined Application) No. 9-326425: “Defectinspecting method and apparatus” (Publication 2) discloses a sampleexamining method for measuring the characteristics of a sample bybringing a mechanical probe into contact with a specific position on thesample surface and applying a voltage to the sample surface with theprobe. This method will be described by referring to FIG. 26. In thismethod, four probes 301, 302, 303 and 304 are contacted to electrodes305, 306, 307 and 308, respectively, on the surface of a sample. Theelectric characteristics among the probes are measured to determine theelectric characteristics of the sample. Initially, the sample surface isscanned by a primary electron beam 309. While observing the samplesurface by picking up secondary electrons 311 with a secondary electrondetector 310, the probes 301, 302, 303, and 304 are moved over theelectrodes 305, 306, 307, and 308. Then, the probe 301 is contacted tothe electrode 305 in the following manner. When the timing immediatelybefore the probe contacts the sample is detected (“pre-contactdetection”) based on the tunnel current or atomic force between theprobe and sample, the movement of the probe is stopped temporarily.Thereafter, the probe is again moved closer to the electrode at a slowerspeed and stopped upon contact. The contact of the probe to the sampleis judged by detecting a contact current with a probe current monitor,or by monitoring a change in potential of the electrode 305 with anenergy filter-equipped secondary electron detector.

One of the most important things when contacting a probe to a specificregion of a sample of the micrometer or sub-micrometer order is avoiddamage to the probe or sample. For this reason, the contact detectiontechniques disclosed in Publications 1 and 2 are at least necessary. Inaddition, to avoid damage to both probe and sample, a means must bedevised to minimize the amount of overshooting when stopping the probe.In Publication 1, it is possible to detect the timing at which the probemakes a contact, but the distance between the probe and the sample priorto contact cannot be known. For these reasons, the overall speed atwhich the probe approaches the sample must be reduced, which results ina longer time before contact is made. On the other hand, in Publication2, the timing immediately before contact with the sample can be known bymaking the pre-contact detection. Therefore, while the speed is loweredimmediately before contact, the time it takes for the probe to makecontact can be reduced by setting the approach speed of the probeimmediately before it makes contact at a high value.

However, the detection of tunnel current requires that the sample beelectrically conductive, so that no detection can be made if the contactregion is an insulator or a floating electrode. In the case of atomicforce detection, the probe must be formed as a cantilever for thedetection of microscopic forces, which is not easy and tends to raisecosts. Furthermore, when detecting tunnel current or atomic force, theprobe must be brought within nanometer-order distances of the samplebefore detection can be made, so a complicated and highly precise probecontrol apparatus capable of both coarse and fine movements isnecessary. In addition, since a piezoelectric element is employed, it isdifficult to maintain a single position after making contact due tocreep phenomena or the like. For these reasons, a means of easily makingthe pre-contact detection is desired.

Further, in the above publications, while the probe's position in aplane parallel to the surface of the sample is monitored through anobserved image, the distance between the probe and the sample can onlybe monitored in a region immediately prior to contact. To enable safetransportation of the probe, however, a technique must be devised whichallows the distance between the probe and the sample to be readilydetermined at any desired position.

When a plurality of probes are used, they must be transported in amanner that they do not interfere with each other. However, theabove-mentioned publications do not disclose any methods fortransporting the probes in a plane parallel to the sample surface.Generally speaking, it is difficult to control the movement of theindividual probes while monitoring their three-dimensional positionalrelationship. Thus, a transportation method is required by whichinterference among the probes can be easily removed.

Conventionally, the transportation of the probe to a positionimmediately above a contact target in a plane parallel to the samplesurface is manually performed by monitoring an observed image. It isdesired, however, to carry out this operation automatically, in order tolessen the burden on the operator. Thus, a transportation technique isrequired by which the coordinates of the probe tip and the contacttarget can be automatically detected.

Accordingly, it is a first object of the present invention to provide aprobe driving method and probe apparatus by which damage to the probeand sample can be curbed by a simple probe control and by which contactcan be made in a short time. A second object of the present invention isto provide a probe driving method and a probe apparatus which allows theoperator to recognize the distance between the probe and the sample,allowing him to easily bring the probe into contact with the sample. Athird object of the invention is to provide a probe apparatus whichautomatically recognizes the coordinates of the probe and sample,allowing the probe to be automatically contacted to a target position onthe sample. A fourth object of the invention is to provide a samplepreparation apparatus by which a removed sample can be reliably preparedwithout it being damaged as a result of contact with the probe. A fifthobject of the invention is to provide a probe apparatus for accuratelyobtaining the characteristics of a sample by contacting a probe to thesample in a reliable manner.

SUMMARY OF THE INVENTION

To achieve the above objects of the invention, in one embodiment,information about the height of a probe relative to the surface of asample is acquired by detecting the shadow of the probe created in anSIM image immediately prior to the contact of the probe to the sample.Based on that information, the drive speed and drive distance of theprobe are controlled so that the probe comes into contact with thesample surface safely and efficiently. In another embodiment of theinvention, the information about the height of the probe relative to thesample surface is acquired based on changes in the relative position ofa probe image and a sample image appearing in a SIM image as the angleof irradiation of an ion beam is varied. Based on that information, thedrive speed and drive distance of the probe are controlled so that theprobe comes into contact with the sample surface safely and efficiently.Further, in another embodiment of the invention, the probe is broughtinto contact with the sample surface in advance and the coordinates ofthe probe tip at that time (position information about the height of theprobe as it contacts the sample surface) are measured and stored. Thestored information is compared with the current height of the probe whenit is located above the sample to thereby acquire accurate probe heightinformation, based on which the probe's drive speed and drive distanceare controlled such that it comes into contact with the sample surfacesafely and efficiently.

Specifically, a probe driving method according to one embodiment of theinvention comprises two steps. In the first step, a sample and probe areirradiated with a beam of charged particles. Secondary particles orreflected particles emitted by the irradiation of the charged particlebeam are detected to produce a sample image including an image of theprobe. The probe is transported toward the sample at a first speed whilethe sample image is monitored. In the second step, the drive speed ofthe probe is switched from the first speed to a slower second speed upondetection of a reduction in luminance in a region adjacent to the probeimage in the sample image. This method allows the probe to be detectedimmediately prior to contact with the sample even over a floatingelectrode or the like.

A probe driving method according to another embodiment of the inventioncomprises four steps. In the first step, a sample and a probe areirradiated with a beam of charged particles at a first angle. Secondaryparticles or reflected particles emitted by the irradiation of thecharged particle beam are detected to produce a sample image includingan image of the probe, and the distance (a first distance) between theposition of the probe tip and a specified position on the sample isdetermined. In the second step, the sample and the probe are irradiatedwith a beam of charged particles at a second angle, which is differentfrom the first angle. Secondary particles or reflected particles emittedby the irradiation of charged-particle beam are detected to produce asample image including an image of the probe. Then the distance (asecond distance) between the positions of the probe tip and theabove-mentioned specified position on the sample is determined on thesample image. In the third step, the distance between the sample and theprobe is calculated based on the first and second angles and the firstand second distances. In the fourth step, the probe is driven toward thesample in accordance with the calculated distance between the sample andthe probe.

A probe driving method according to another embodiment of the inventioncomprises three steps. In the first step, the coordinates of the tip ofa probe, when it is in contact with the sample, in a directionintersecting the sample surface are measured and recorded by ameasurement means. In the second step, the current distance between theprobe and the sample is determined based on the recorded probe tipcoordinates and the current probe tip coordinates measured by themeasurement means. In the third step, the probe is brought into contactwith the sample while controlling the probe drive distance and drivespeed in accordance with the determined distance.

A probe apparatus according to another embodiment of the inventioncomprises; a movable sample base on which a sample is to be placed; acharged particle optical system for irradiating the sample with a beamof charged particles; a detector for detecting secondary particles orreflected particles emitted or reflected by the sample as it isirradiated with the beam of charged particles; a probe to bemechanically contacted to the sample surface; a probe control apparatusfor controlling the driving of the probe, a display apparatus fordisplaying the information detected by the detector in the form of animage; and a detection information analyzing apparatus for analyzing theinformation detected by the detector. The probe control apparatuscontrols the probe driving apparatus based on the result of analysis bythe detection information analyzing apparatus.

The detection information analyzing apparatus may comprise a functionfor detecting a change in luminance in a region adjacent to the probe inthe image.

When the detection information analyzing apparatus detects a reductionin luminance in a region adjacent to the probe while the probe is beingtransported toward the sample at the first speed, the probe controlapparatus switches the drive speed of the probe moving toward the samplefrom the first speed to a slower, second speed.

When the detection information analyzing apparatus detects a reductionin luminance in a region adjacent to the probe while the probe is beingtransported toward the sample at the first speed, the probe controlapparatus switches the drive speed of the probe moving toward the samplefrom the first speed to the slower, second speed. When the detectioninformation analyzing apparatus detects a sudden increase in luminancein the region adjacent to the probe while the probe is being transportedtoward the sample at the second speed, the probe control apparatusterminates the driving of the probe.

The detection information analyzing apparatus may comprise a functionfor calculating the distance between the probe and the sample based onthe coordinates of the tip position of the probe and the specificposition on the sample in a plurality of images obtained by irradiatingthe probe and the sample surface with the charged particle beam atdifferent angles.

The probe apparatus may comprise a probe for transferring a separatedand removed part of a sample to another member, and a sample holderretaining tool for retaining a sample holder that holds the removedsample.

The display apparatus may display information relating to the distancebetween the sample surface and the probe.

A probe apparatus according to another embodiment of the inventioncomprises: a movable sample base for mounting a sample; a chargedparticle optical system for irradiating the sample with a beam ofcharged particles; a detector for detecting secondary particles orreflected particles emitted or reflected by the sample as it isirradiated with the charged particle beam; a display apparatus fordisplaying the information acquired by the detector in the form of animage; a probe to be mechanically brought into contact with the samplesurface; a probe control apparatus for controlling the driving of theprobe; and a probe reference coordinates recording apparatus forrecording the coordinates of the probe tip which are obtained bycontacting the probe to the sample in advance. The probe controlapparatus controls the drive distance and speed of the probe based onthe coordinates recorded in the probe reference coordinates recordingapparatus and the coordinates of a position of the sample where theprobe is to be brought into contact with the sample.

A probe apparatus according to another embodiment of the inventioncomprises a movable sample base for mounting a sample; a chargedparticle optical system for irradiating the sample with a beam ofcharged particles; a detector for detecting secondary particles orreflected particles emitted or reflected from the sample as it isirradiated with the charged particle beam; a display apparatus fordisplaying the information detected by the detector in the form of animage; a plurality of probes to be mechanically brought into contactwith the sample surface; and a probe control apparatus for transportingthe probes parallel to the sample surface such that the individualprobes are transported within the individually different, specificdistances until they reach the sample surface.

In the case where there are provided a plurality of probes and a probeelectric control apparatus for performing electric control such as theapplication of a voltage to the probe or the measuring of the electriccharacteristics of the sample, the probe electric control apparatus maycomprise an inter-probe, electrically controlled switching apparatus forswitching between electric control of any desired probe and electriccontrol of any other desired probes. In this way, probe symmetry can beensured and thus probe control can be facilitated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example of a sample preparationapparatus according to the invention.

FIG. 2 shows a SIM image at the time when a probe is away from thesample surface.

FIG. 3 shows a SIM image at the time when the probe is close to thesample surface.

FIG. 4 shows a SIM image at the time when the probe is in contact withthe sample surface.

FIG. 5 shows the relationship among luminance in a monitored region,probe-to-sample distance, elapsed time, and a probe's approaching speed.

FIG. 6 illustrates an electric field for inducing secondary electrons ina plane perpendicular to the sample surface.

FIG. 7 illustrates an electric field for inducing secondary electrons ina plane parallel to the sample surface.

FIG. 8 shows an example of the display of probe height on a displayapparatus in the apparatus according to the invention.

FIG. 9 schematically shows an example of a secondary electroninformation analyzing apparatus according to the invention.

FIG. 10 illustrates the concept of probe control in the apparatusaccording to the invention.

FIG. 11 illustrates the individual steps of the process of preparing aremoved sample by means of the apparatus according to the invention.

FIG. 12 illustrates an example of the manner in which parts areassembled for preparing a microscopic machine according to theinvention.

FIG. 13 shows the positional relationship between the probe and thesample in the case of FIBθ1 diagonal irradiation according to theinvention.

FIG. 14 shows a SIM image in the case of FIBθ1 diagonal irradiationaccording to the invention.

FIG. 15 shows the positional relationship between the probe and thesample in the case of FIBθ2 diagonal irradiation according to theinvention.

FIG. 16 shows a SIM image in the case of FIBθ2 diagonal irradiationaccording to the invention.

FIG. 17 schematically shows an example of the secondary electroninformation analyzing apparatus for FIB diagonal irradiation accordingto the invention.

FIG. 18 illustrates a method of automatically acquiring the distance tobe traveled by a probe to a position immediately above a targetaccording to the invention.

FIG. 19 shows a block diagram of an example of the FIB sample diagnosisapparatus according to the invention.

FIG. 20 illustrates a method of transporting a plurality of probes in aplane parallel to a sample in a non-interfering manner according to theinvention.

FIG. 21 shows a flowchart of the procedure for realizing probe contactaccording to the invention.

FIG. 22 illustrates an example of the manner in which wiring breakage isdetected by the FIB sample diagnosis apparatus according to theinvention.

FIG. 23 shows a block diagram of an example of the electron beam samplediagnosis apparatus according to the invention.

FIG. 24 illustrates a technique for determining the distance betweenprobe and sample by an open-loop control according to the invention.

FIG. 25 illustrates a preliminary contact according to the invention.

FIG. 26 schematically shows a conventional sample diagnosis apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention will be hereafter described in detail by referring to theattached drawings.

Embodiment 1

FIG. 1 shows a block diagram of an embodiment of the sample preparationapparatus according to the present invention for preparing a microscopicanalysis sample or a microscopic device by a focused ion beam (FIB).

A sample 4 to be analyzed, such as a semiconductor wafer or chip, ismounted on a movable sample base 5 and positioned by a sample basecontrol apparatus 6. The sample base control apparatus 6 controls theposition of the sample base 5 for determining the diagnosis position ofthe sample 4. A removed sample holder 18 for mounting a removed sampleis fixed by a removed sample holder retainer 17 on the sample base 5. Aprobe 7 detects device characteristics such as the resistance andcurrent in the sample 4 as well as supplying voltage thereto, under thecontrol of a probe electric control apparatus 13. The probe 7 is drivenby a probe driving apparatus 8 which is controlled by a probe controlapparatus 9.

An ion beam optical system 1 for irradiating the sample 4 with a beam ofions emitted by an ion source 1000 comprises: a beam limiting aperture1001 for limiting the ion beam emitted by the ion source to apredetermined size; a focusing lens 1002 for focusing the ion beam; adeflector 1003 for deflecting the ion beam to a predetermined positionon the sample; and an objective lens 1004 disposed in front of thesample for irradiating the sample with a deflected beam. The ion beamoptical system 1 is controlled by an ion beam control apparatus 2.Secondary electrons generated when the sample or the probe is irradiatedby the ion beam 3 from the ion beam optical system 1 are detected by asecondary electron detector 10. The thus detected secondary electronsare input to a display apparatus 12 as a luminance signal in synchronismwith a scan signal applied to the deflector 1003, whereby an image ofthe sample surface and/or the image of the probe 7 are displayed on thedisplay apparatus 12. In this process, the probe control apparatus 9 iscontrolled by a secondary electron information analyzing apparatus 11identifying a certain portion of the secondary electron information, aswill be described in detail later. A deposition gas source 14 iscontrolled by a deposition gas source control apparatus 15. It suppliestungsten carbonyl gas, for example, above the sample 4, where the ionbeam 3 is irradiated to form a tungsten film on the irradiated portion,thereby forming a protective film, bonding the probe 7 and the removedsample, or bonding the removed sample and the removed sample holder 18.

The ion beam control apparatus 2, deposition gas source controlapparatus 15, probe electric control apparatus 13, probe controlapparatus 9, secondary electron information analyzing apparatus 11,sample base control apparatus 6, and display apparatus 12 are controlledby a calculation processing unit 16. The calculation processing unit 16may be realized in a personal computer or a workstation comprising theion beam control apparatus 2, deposition gas source control apparatus15, probe electric control apparatus 13, probe control apparatus 9,secondary electron information analyzing apparatus 11, and sample basecontrol apparatus 6.

The method of driving the probe will be described by referring to FIGS.2-5. The approach and contact of the probe to the sample surface isexplained. FIGS. 2-4 each show a secondary electron image displayed onthe display apparatus 12. Numeral 51 designates a pad with which theprobe 7 is to be brought into contact. Numeral 52 designates aninsulating region. Usually, the distance between the probe 7 and thesample 4 cannot be directly determined based on the observed imagedisplayed on the display apparatus 12. In order to curb damage to boththe probe 7 and the surface of the sample 4 as the former contacts thelatter, the speed at which the probe 7 approaches the sample surfaceshould desirably be reduced. This means, however, that, when thedistance between the probe and the sample is unknown, the probe approachspeed has to be reduced throughout the entire distance of probetransportation, thereby requiring a long time before the probe contactoperation can be completed. If the pre-contact detection can be made,the probe speed can be controlled in accordance with its distance fromthe sample surface, such that contact can be made in a short timewithout damage. In the present embodiment of the invention, a shadow 54of the probe 7 is utilized for the pre-contact detection.

In the present embodiment, a secondary electron signal produced by apositive ion FIB irradiation is shown on the display apparatus 12 as animage. At this time, the probe itself is connected to the probe electriccontrol apparatus 13, so that the probe is not charged even whenirradiated with the FIB. However, when the contact pad 51 iselectrically floating, the pad 51 is positively charged. This is becausethe ingress of positive ions and the emission of the negative secondaryelectrons constitute the dominant process. As a result, in a regionwhere the probe 7 is sufficiently away from the sample surface, thesecondary electrons emitted by the sample by the FIB irradiation aredrawn back to the sample before they arrive at the secondary electrondetector, so that the secondary electron signal, i.e., the luminance inthe display apparatus 12 appears dark, as shown in FIG. 2.

As the probe 7 approaches the sample surface, the probe increasinglyblocks the arrival of the secondary electrons emitted by the samplesurface near the probe at the secondary electron detector 10. Thus, theshadow 54 is observed, as shown in FIG. 3.

Specifically, the shadow 54 is observed for the following reasons. FIG.6 schematically shows the induction electric field of the secondaryelectron detector 10 in the presence of the probe 7, as seen from adirection parallel to the surface of the sample 4. The secondaryelectrons generated by ion beam irradiation at a position 83 on thesample surface away from the probe 7 are drawn into the secondaryelectron detector 10 by its induction electric field indicated by anequipotential surface 84. But secondary electrons generated at aposition 81 on the sample surface below the probe 7 are not easily drawninto the secondary electron detector 10 because the induction electricfield of the secondary detector 10 is blocked by the probe 7. As aresult, the SIM image appears dark. FIG. 7 schematically shows theelectric field as the probe 7 approaches the sample surface, as seenfrom a direction perpendicular to the sample surface. Electronsgenerated at a position 83 on the sample surface away from the probe 7are accelerated by the induction electric field of the secondaryelectron detector 10 indicated by the equipotential surface 84, and fedinto the secondary electron detector. If the probe 7 is near the samplesurface, however, the induction electric field 84 cannot easily expandnear the probe. Thus, secondary electrons generated at regions 86 and 87on the sample surface near the probe are not readily accelerated towardthe secondary electron detector 10 and are therefore not detected by thesecondary electron detector 10, resulting in a dark shadow on thesecondary electron image. The shadow 54 of FIG. 3 appears when, forexample, the approaching probe 7 is about 20 μm from the surface of thesample.

As the probe 7 further approaches the sample and contacts the pad 51,the charge on the pad 51 is relaxed by the electrons injected by theprobe 7, thereby increasing the luminance of the pad 51 on the observedimage, as shown in FIG. 4. The upper-left part of FIG. 5 shows a changein luminance monitored in a luminance monitored region 53 designated bya mouse, for example, on the display apparatus 12, as shown in FIG. 2.In FIG. 5, the horizontal axis indicates the z-transportation distanceof the probe, while the vertical axis indicates the luminance of theluminance monitored region 53. Position z1 corresponds to the positionof the probe in a region, as in FIG. 2, where the probe is sufficientlydistanced away from the sample. Position z2 corresponds to the positionof the probe in a region where a shadow is observed as shown in FIG. 3.Position z3 is the sample surface position corresponding to FIG. 4.

The distances are, for example, about 500 μm between positions z3 andz1, and about 10 μm between positions z3 and z2. At position z3, theprobe 7 contacts the sample such that the charge on the contact pad 51is relaxed, resulting in a sudden increase in luminance in the observedimage.

If a voltage which is positive relative to that of the sample 4 isapplied to the probe 7 by the probe electric control apparatus 13, theprobe 7 draws secondary electrons such that the field of view isdarkened overall, making it difficult to identify the shadow 54 of theprobe. Conversely, if a voltage negative relative to that of the sample4 is applied to the probe 7, the probe 7 can be observed more brightlyand so the shadow 54 can be more easily identified.

By utilizing the above phenomena, the probe can be efficiently contactedin a flow as shown in the lower-right portion of FIG. 5, in which thehorizontal axis indicates the time since the start of approach of theprobe to the sample. Against the time axis, the relationship betweenchanges in luminance I in the luminance monitored region 53 and the setprobe approach speed v is shown. In an initial region where theluminance I is such that Is<I<Ic, the probe is brought closer to thesample with an approach speed v set at a high speed (vh). As theluminance I in the luminance monitored region 53 starts to drop (t1),and when I<Is (t2), the probe approach speed v is changed to a low speed(v1). Upon contact, the luminance I increases and when I>Ic, the probeis stopped by setting its approach speed v at zero (t3). Is and Ic areset with respect to luminance I (Z1), that is the luminance in a regionZ1 where the probe is sufficiently away from the sample surface, suchthat Is=0.8×I(Z1) and Ic=2×I(Z1). Through the above-described flow, theprobe can be brought into contact with the sample in a short timewithout damaging either. When there is not enough luminance change inthe luminance monitored region 53, the luminance I can be differentiatedwith respect to distance as shown in the lower-left part of FIG. 5,thereby emphasizing the variation and facilitating the acquisition ofpositional information. Displaying a distance-differentiated graph ofthe luminance I on the display apparatus 12 helps the operator identifythe probe position.

The above example assumed the presence of the contact pad 51 for ease ofexplanation. However, the shadow 54 of the probe is observed in theabsence of the contact pad, so that the timing immediately before theprobe makes contact can be monitored. Namely, in this flow, thepre-contact detection can be made even when the sample underinvestigation is an insulator. Furthermore, this system is capable ofmaking the pre-contact detection at a stage when the distance betweenthe probe and the sample surface is greater than that at which thepre-contact detection is made in the tunnel current detection system oratomic force detection system. Thus, the required level of probe brakingaccuracy is not so high. Accordingly, this system allows a probe drivingapparatus or probe control apparatus to be manufactured inexpensively.

In the case where the sample is electrically conductive, the probe canbe safely contacted with the sample through the following flow. First, abias voltage is applied to the probe 7 via a high resistance. When theprobe 7 is far away from the sample 4, the luminance monitored regionnear the probe is not influenced by the probe 7 and exhibits thesecondary electron luminance of the sample itself. As the probe 7approaches the sample 4, the luminance of the luminance monitored regionnear the probe decreases, due to the inability of the secondary electroninduction electric field of the secondary electron detector 10 to expandnear the probe, as described with reference to FIGS. 6 and 7. Then theprobe approach speed is lowered. The probe 7 further approaches thesample 4 and eventually comes into contact with the sample 4, whereuponthe potential of the probe 7 drops to that of the sample via the highresistance. As a result, the blocking of the second electron inductionelectric field is relaxed and the sample luminance near the probe isbrought back to normal. By detecting this, the contact of the probe 7 tothe sample 4 can be determined, whereupon the driving of the probe isterminated. Thus, in the case of a conductive sample as well, the probecan be brought into contact with the sample in an efficient manner bythe apparatus according to the present invention.

Because the change in the luminance I in the luminance monitored region53 can be related to the distance between the probe 7 and the sample,the information about the height of the probe above the sample surfacecan be displayed on the display apparatus 12, as shown in FIG. 8.Specifically, a display screen 3001 can include an SIM image displayportion 3007, a probe height display portion 3002, and a probe-to-sampledistance display portion 3003 as subordinate screens. In the probeheight display portion 3002, a sign 3005 indicating the sample surface,a sign 3004 indicating the probe, and a size display bar 3006 indicatingthe size are displayed. A specific value of the probe height isindicated in the probe-to-sample distance display portion 3003. Thesescreens allow the operator to recognize the distance between the probeand the sample intuitively.

FIG. 9 is a drawing for the explanation of the flow of signaltransmission and reception involving the secondary electron informationanalyzing apparatus 11. An image is generated in an SIM image generatingunit 21 based on the deflector scan signal from the ion beam controlapparatus 2 and the secondary electron luminance information from thesecondary electron detector 10, and is displayed on the display unit 12.By designating a luminance monitored region 53 (see FIGS. 2-4) by meansof a pointing device such as a mouse, the coordinates of the luminancemonitored position are set in a monitored portion luminance accumulatingunit 22, where a luminance signal corresponding to the coordinate regionis accumulated. The accumulated luminance information is compared in aluminance comparison unit 23 with a comparative luminance (such as Isand Ic in FIG. 5) which is set in advance in a comparative luminanceinformation unit 24. As a result, the height information is obtained,and an appropriate approach speed is set in a calculation processingunit 16. Based on the resultant signal, the probe control apparatus 9controls the driving of the probe 7, as described with reference to FIG.5. The height information from the luminance comparison unit 23 isdisplayed on the display apparatus 12. In this manner, efficient probecontrol can be effected.

FIG. 10 visually illustrates the overall flow of the signal. Thesecondary electrons generated as FIB 3 scans are fed into the secondaryelectron detector 10. The luminance of the luminance monitored region 53is analyzed by the secondary electron information analyzing apparatus11, and the distance between probe and sample is calculated based on theresultant luminance information and displayed on the display apparatus12. The secondary electron information analyzing apparatus 11 furthercalculates an appropriate probe drive speed suitable for theprobe-to-sample distance, and gives a speed instruction to the probecontrol apparatus 9. In response, the probe control apparatus 9 controlsthe probe driving apparatus 8, by which the probe 7 is driven, such thatthe probe is brought into contact with the sample in an efficient andsafe manner. At this time, the change-over switch 2401 is connected tothe secondary electron information analyzing apparatus 11. When theprobe approach is to be made manually, the change-over switch 2401 isconnected to a probe operating apparatus 2400. The probe operatingapparatus 2400 comprises an input device such as a push button,joystick, mouse, or the like. When the probe operating apparatus 2400 isselected by the change-over switch 2401, the probe is operated manuallyby the operator viewing the probe height information in the displayapparatus 12. The manual operation can be facilitated by providing afunction, through an indicator or a buzzer, for example, for notifyingthe operator of a luminance or a change in luminance detected by thesecondary electron information analyzing apparatus 11 at which the speedshould be changed.

FIG. 11 illustrates a method of preparing a sample using theabove-described apparatus according to an embodiment of the invention.

Initially, marks 403 and 404 for identifying the target position areformed by irradiation by a FIB 3. Rectangular openings 401 and 402 arethen formed in a sample 4 outside either opening (FIG. 11(a)). Then, arectangular groove 406 is formed by FIB 3, leaving a support portion 405(FIG. 11(b)). Thereafter, the sample base 5 is tilted so that the samplesurface can be irradiated with FIB 3 diagonally to thereby form anangled groove 408. As a result, a removed sample 407 connected with thesample 4 only via the partial support portion 405 is formed (FIG.11(c)). The sample base is then brought back to the original angle, andthe probe driving apparatus 8 is controlled by the probe controlapparatus 9 such that the probe 7 is brought into contact with a part ofthe removed sample 407 through the probe driving flow described withreference to FIG. 5.

While the support portion 405 of the removed sample is later cut by FIB,the cutting should desirably be done in a short time in light of thepossibility of probe drift, for example. Therefore, the volume of thesupport portion should be minimized. This, however, gives rise to thefear that the support portion 405 might be damaged by contact with theprobe 7. Thus, the probe is brought into contact by the above-describedprobe control method in order to minimize damage. The contacting probe 7and the removed sample 407 are immobilized by means of an IBAD film 409(FIG. 11(d)). Then, the support portion 405 is cut by FIB 3 (FIG.11(e)).

The removed sample 407 is thus cut from the sample 4 and removed as theprobe 7 is raised by the probe driving apparatus 8 (FIG. 11(f)). Thethus removed sample 407 is contacted to a groove 411 formed in a removedsample holder 18 (FIG. 11(g)). This contact should be made with asufficiently small speed lest the removed sample 407 be damaged ordetached at IBAD film portion 409 and thus lost. Thus, theabove-described contact method is required. When the removed sample isbrought closer to the removed sample holder, a shadow of the removedsample corresponding to the shadow 54 of the probe described byreferring to FIG. 3 appears. For this reason, the height of the removedsample can be recognized by monitoring the luminance near the removedsample, so that the probe approach speed can be controlled as shown inFIG. 5. After making contact, the probe and the sample are immobilizedby means of an IBAD film 412 (FIG. 11(h)). After immobilization, theprobe-connected portion is irradiated with FIB, sputtering takes place,and the probe is separated from the removed sample 407 (FIG. 11(i)).When the removed sample 407 is to be used as a TEM sample, the sample isagain irradiated with FIB 3, and an observation region 410 is processedto a thickness of 100 nm or less in a finishing process (FIG. 11(j)).When the sample is to be used for preparing a sample for other analysisor measurement purposes, the process of thinning the observed region isnot necessarily required.

This technique can be applied not only to the preparation of an analysissample but also to the preparation of a device. For example, a unit cellmay be removed from a sample substrate on which device unit cells areprepared, using the same flow as for the removal of the removed sample407. The removed unit cell may be transplanted to a part of anotherdevice to create a new device. Since in this case the microscopic unitcell must be removed, transported and fixed without being damaged, theabove-described probe driving method, which is capable of making thepre-contact detection, can be effectively used.

The technique can also be applied to the manufacture of microscopicmachines. For example, as shown in FIG. 12, a gear part 151 of amicroscopic machine of the order of microns formed on a substrate by FIBprocessing or lithography may be removed by the above-described removalflow and inserted into a bearing 152. Thus a microscopic component canbe assembled and a microscopic machine can be produced. In themanufacture of such a machine, the microscopic gear part 151 and thebearing 152 must be removed, transported and fixed without damage. Thus,the above-described probe driving method can be effectively used.

Embodiment 2

The process of monitoring the probe-to-sample distance will be describedby referring to FIGS. 13-16. While the pre-contact detection techniquewas described in Embodiment 1, in the present embodiment, the method ofidentifying the current distance between the probe and the sample willbe described.

FIG. 13 schematically shows the relationship among an ion emittingportion 62 of the FIB optical system, a probe 7 and a sample 4. FIG. 14shows an observed image displayed on a display apparatus 12. Numeral 61designates a specific position on the surface of the sample that isindicated by a marking produced by FIB processing. The position,however, may be indicated by a structural feature on the sample. Whenthe probe 7 and the sample 4 are irradiated with the FIB in an inclinedmanner such that the angle formed by the beam and the optical axis ofthe system is θ1, the distance between the tip of the probe 7 and themarking 61 is observed as d1 in the observed SIM image, as shown in FIG.14. When the FIB is inclined to the side opposite to the case of FIG. 13with an angle θ2, as shown in FIG. 15, the distance between the tip ofthe probe and the marking 61 is observed as d2 on the opposite side inthe observed SIM image, as shown in FIG. 16. Based on these twoobservation results, the distance h between probe and sample can beexpressed by the following equation:h=(d 1+d 2)·cos θ1·cos θ2/sin(θ1+θ2)  (1)

When the FIB angles θ1 and θ2 are both equal to θ, equation (1) can besimplified to:h=(d 1+d 2)/(2·tan θ)  (2)

The relationship between the deflection voltage V and the FIB angle θcan be obtained as follows. A deflection constant Cd prescribed by theapparatus is defined as follows:Cd=dV/dx  (3)where x is the deflection amount.

When the distance between a deflection center and the sample surface isassumed to be Lw,Lw·tanθ=x  (4)so that, when the deflection voltages corresponding to the angles θ1 andθ2 are V1 and V2, respectively,θ1=arctan(V 1/(Lw−Cd))  (5)θ2=arctan(V 2/(Lw−Cd))  (6)

Thus, the distance h between probe and sample can be determined based onV1, V2, d1 and d2. When V1=V2−V(θ1=θ2=θ),h=(d 1+d 2)·Lw·Cd/(2V)  (7)

Thus, by measuring the distances d1 and d2 during deflection by thedeflection voltage V, the distance h between probe and sample can bedetermined.

The thus determined distance h and the positional relationship betweenprobe and sample can be displayed in real time in subordinate screens onthe display apparatus 12, such as those shown in FIG. 8. In this way,the operator can visually recognize the current distance between probeand sample.

While in the above example, the FIB was deflected on either side of theoptical axis for improving the distance-recognition performance, it isalso possible to recognize the distance by irradiation normal to thesample surface and diagonally on one side.

This case is the same as when 02=0, so that, when the deflected amountat the time of vertical irradiation is d2,h=(d 1+d 2)/tanθ1  (8)

When the deflection voltage is V1, we haveh=(d 1+d 2)·Lw·Cd/V 1  (9)

The thus obtained distance between probe and sample can be displayed onthe display apparatus 12 as described in Embodiment 1 with reference toFIG. 8, thus allowing the operator to recognize the distanceintuitively.

FIG. 17 is a drawing for the explanation of the signal exchangeinvolving the secondary electron information analyzing apparatus 11during the diagonal FIB irradiation. An image is generated by the SIMimage generating unit 21 based on the deflector scan signal from the ionbeam control apparatus 2 and the secondary electron luminanceinformation from the secondary electron detector 10. The image isdisplayed on the display apparatus 12. Based on this SIM image,displacement amounts d1 and d2 during deflection by V1 and V2 areobtained by a probe displacement amount recognizing unit 2501. Based onV1, V2, d1 and d2, a probe height h is calculated by an intervalidentifying apparatus 2502. The height h is displayed on the displayapparatus 12. An appropriate speed for the probe height h is set by aprobe speed selection unit 2503 from which a signal is sent to the probecontrol apparatus 9.

In the present embodiment, the current distance h between probe andsample can be detected, so that the probe 7 can be prevented fromcrashing into the sample 4 when the sample base or probe is moving.Further, this embodiment is also effective in removing interferenceamong probes when more than one probe is used.

Embodiment 3

Referring to FIG. 18, a method of controlling the probe such that theprobe tip is transported parallel to the sample surface and broughtimmediately above a target position of the sample will be described.FIG. 18 shows an SIM image. Numeral 7 designates a probe, 73 and 74designate marks formed by a FIB, and 78 designates an FIB processedopening. Numeral 75 designates a sample to be removed. The object of theprobe operation is to bring the tip 71 of the probe into contact with aprobe connection portion 72 of the removed sample 75. A reference image76 of the probe tip is acquired from the SIM image in advance. Numeral71 designates the position of the probe tip. Numeral 77 designates anFIB mark reference image for identifying the probe connection portion.By matching the SIM image against the reference images 76 and 77, theposition corresponding to the probe tip position in the reference image76 is identified as the position of the probe tip 71. Likewise, theposition corresponding to the position of the probe connection portionin the reference image 77 is identified as the position of the probeconnection portion 72. Based on these items of information, displacementamounts Lx and Ly between the current probe tip 71 and the probeconnection portion 72 in a plane parallel to the sample surface can beobtained. The probe control apparatus 9 drives the probe drivingapparatus 8 by these amounts Lx and Ly, so that the probe tip 71 can bebrought immediately above the probe connection portion 72. Thus, bycarrying out this control method, the probe tip can be automaticallytransported to the target position.

Embodiment 4

Hereafter, an embodiment will be described in which the invention isapplied to a sample diagnosis apparatus in which the probe is contactedto a sample in an FIB apparatus in order to evaluate the electriccharacteristics of a sample based on the distribution of secondaryelectron signal luminance and the current/voltage characteristics asmeasured by the probe.

FIG. 19 shows an example of the constitution of the sample diagnosisapparatus. A sample 4 to be diagnosed, such as a semiconductor wafer orchip, is mounted on a movable sample base 5. The sample 4 is positionedfor diagnosis by a sample base control apparatus 6 by which the positionof the sample base 5 is controlled. Four probes 801, 802, 803 and 804(although in the drawing probes 802, 803 and 804 are not shown to beconnected to the probe electric control apparatus 13, in fact they are)for supplying voltage to the sample 4 or measuring the resistance,current or the like of the sample, under the control of the probeelectric control apparatus 13, are driven by probe driving apparatus805, 806, 807 and 808 (although in the drawing the apparatus 806, 807,and 808 are not shown to be connected to the probe control apparatus 9,in fact they are), under the control of the probe control apparatus 9.

The surface of the sample 4 and the probe are observed by detectingsecondary electrons with a secondary electron detector 10 and displayingan image of the sample and probe on the display apparatus. The electronsare generated as the ion beam 3 from the ion beam optical system 1,under the control of the ion beam control apparatus 2, irradiates thesample surface and probe. The probe control apparatus 9 is controlled bythe secondary electron information analyzing apparatus 11, whichidentifies specific information from the secondary electron information.A deposition gas source 14 is controlled by a deposition gas sourcecontrol apparatus 15 and supplies tungsten carbonyl gas, for example,above the sample 4. The sample 4 is irradiated with the ion beam 3 sothat a tungsten film is formed at the irradiated portion, therebyallowing the wiring to be modified or an electrode pad to be formed.

The ion beam control apparatus 2, deposition gas source controlapparatus 15, probe electric control apparatus 13, probe controlapparatus 9, secondary electron information analyzing apparatus 11,sample base control apparatus 6, and display apparatus 12 are controlledby a calculation processing unit 16. The calculation processing unit 16may be realized on a personal computer or a workstation comprising theion beam control apparatus 2, deposition gas source control apparatus15, probe electric control apparatus 13, probe control apparatus 9,secondary electron information analyzing apparatus 11, and sample basecontrol apparatus 6.

Referring to FIG. 20, a method of transporting a plurality of probeswill be described. FIG. 20 shows the positional relationship among asample 4 and probes 801, 802, 803 and 804 as seen from a directionparallel to the surface of the sample 4. For simplicity, the distancebetween each probe and the sample will be hereafter referred to as aprobe height. In the case where a plurality of probes exist, as in FIG.20, it is necessary that when one probe moves in a plane (“XY plane”)parallel to the sample surface, that probe does not interfere with theother probes. When the probes are in the FIB field of view, this can beensured by utilizing the probe height monitor used in Embodiment 2.However, when there is a probe outside of the FIB's field of view, it isdifficult to recognize possible interference among the probes. Inparticular, it should be noted that the probe is replaced as anexpendable item when the influence which oxidation on the probe surface,for example, has on the measurement of electric characteristics cannotbe disregarded anymore. In this light, the height of the probe tipposition cannot be accurately recognized solely by means of the absolutecoordinates of the probe driving apparatus, and therefore possibleinterference among the probes cannot be easily recognized.

In the present embodiment, the height of the probe 801 is limited whenit is transported in the XY plane even outside of the FIB field of viewin order to ensure that the probes do not interfere with each other.Specifically, the probe height is limited within a region of h1 to h0.Similarly, the transportation of probe 802 is limited within a region h2to h1, probe 803 within a region h3 to h2, and probe 804 within a regionh4 to h3. When the probe comes into contact with the sample, the probesare lowered to a region below h0. Namely, each probe is located onlywithin the individually specific height (such as h1 to h0 in the case ofthe probe 801), or below h0. The heights h0, h1, h2, h3 and h4 aredetermined by the size of the probe structural portion and the probeattachment tolerance.

By thus setting the specific height of each probe in its intra-XY planemovement, it becomes possible to bring each probe immediately above thetarget position without interfering with other probes. After the probeis located immediately above the target position, the probe is broughtcloser to the sample 4 until it contacts the sample in the region of h0.It should be noted, however, that for the intra-XY plane fine movementfor the purpose of fine-adjustment of intra-XY plane position, the probemay be moved within the region of h0, for there is no fear of the probeinterfering with other probes there. In other words, for fine-adjustmentpurposes, the probe does not have to be brought up to the individuallyassigned height for transportation. Thus, this probe control method canremove interference among the probes when more than one probe issimultaneously moved, so that the probes can be transported in a shorttime.

FIG. 21 shows a flowchart of the contact flow based on the above method.First, the sample base is transported into the FIB observation field ofview at the target position for measurement (S11). Then, the probe 801is introduced into the FIB field of view through the following flow bythe intra-XY plane non-interfering transportation method for the probe(see FIG. 20). Initially, it is determined whether h0<(height of probe801)<h1 (S12). If outside this range (N), the probe 801 is in the regionbelow h0, so the probe 801 is raised (S13). Herein the direction inwhich the probe approaches the sample is referred to as descent, and theopposite, separating direction is referred to as ascent. As the probe801 enters the region h0 to h1 (Y), the probe 801 is introduced into theFIB field of view by transporting it in the XY plane (S14).

Next, the probe 801 is transported immediately above the target positionby the method of obtaining the coordinates of the probe tip position andcontact target position based on the reference images, as described byreferring to FIG. 18. This is done through the following flow. First,the target position coordinates (Xs1, Ys1) are obtained by detecting thecoordinates of the target position by image matching (S15).

The probe tip coordinates (Xp1, Yp1) are then obtained by detecting thecoordinates of the tip of the probe 801 by image matching (S16). Basedon the difference between these two sets of coordinates, thetransportation distance (Lx, Ly)=(Xs1−Xp1, Ys1−Yp1) in the XY plane iscalculated (S17). Then, it is determined whether the transportationdistance in the XY plane is less than the tolerance amounts (LX<Lxe,Ly<Lye) (tolerance amounts (Lxe, Lye) are set in advance) (S18). If theresult of this determination is (N), the probe 801 is transported in theXY plane (Lx, Ly) (S19). In this way, the probe tip position is broughtto within the tolerance range immediately above the target position.

The approach speed of the probe 801 is then set at a high speed (such as1 mm/s) (S20). The luminance of the SIM image is adjusted so that thesample surface can be observed on the display apparatus 12 and that atthe same time the probe luminance does not saturate (S21). The luminancemonitoring region is then set near the probe 801, as shown in FIG. 2(S22), and luminance monitoring is initiated (S23). As the probe 801approaches the sample (S24), it is determined whether the monitor regionluminance I is less than a preset threshold luminance Is (S25). If theresult of determination is (N), the approach of the probe continues atthe high speed and, when the monitored region luminance I falls below Is(Y), the approach speed of the probe is switched to a slow speed (suchas 0.5 μm/s) (S26). Then, it is determined whether the monitored regionluminance I is greater than a preset threshold luminance Ic (S27). Ifthe result of determination is (N), the approach of the probe continuesand, when the monitored region luminance I rises above Ic (Y) andcontact is detected, the approach of the probe 801 is terminated (S28).

Then the coordinates of the probe tip (Xp1, Yp1) are again obtained bydetecting the coordinates of the probe tip by image matching (S29).Based on the difference between these coordinates and the coordinates ofthe target position (Xs1, Ys1) obtained in the step of detecting thecoordinates of the target position (S15), the transportation distance(Lx, Ly)=(Xs1−Xp1, Ys1−Yp1) in the XY plane is calculated (S30). Next,it is determined whether the transportation distance in the XY plane isless than the tolerance (Lx<Lxe, Ly<Lye) (S31). If the result is (N),the probe 801 is raised by a short distance (S32), transported in the XYplane (Lx, Ly) (S33), and the approach of the probe 801 is repeated atthe slow speed (S26). Eventually, when the condition of thetransportation distance in the XY plane being less than the tolerance(Lx<Lxe, Ly<Lye) is satisfied (Y), the contact of the probe tip to thetarget position is completed. Thereafter, the sample characteristics aremeasured based on SIM contrast and probe current, for example, in theprobe electric control circuit 13 (S34). When a plurality of probes areused, the probe 801 is replaced with the second or other subsequentprobes and the entire measurement process is repeated (S35).

The above flow can be conducted entirely automatically once the probetip reference image and the contact target position reference image areset and the luminance monitored position is designated in advance. Thusthe probe can be automatically brought into contact with the sample andthe burden on the operator can be reduced.

Referring now to FIG. 22, an example in which a wire breakage portion ofa device wiring on the surface of a sample is identified by theapparatus according to the invention will be described. In the drawing,numeral 101 designates a measuring device, numeral 102 a metal wiring onthe sample surface, and numeral 103 a metal wiring inside the sample.The metal wirings 102 and 103 are connected by a connection plug 104 ina chain structure, as shown. As shown, there is breakage in a connectionplug 105.

The probe 801 is brought into contact with an electrode pad 106 on thisdevice in the manner described in the above flow. Since a wiring region107 down from the breakage portion is electrically floating, it ischarged by FIB irradiation and appears dark in a secondary electronimage. This is due to the following reasons. In the present embodiment,positive gallium ions are used in the FIB irradiation. As the floatingportion is irradiated with positive ions in the FIB, positive chargesare injected. At the same time, secondary electrons are emitted, so thatthe floating portion is further positively charged. When the floatingportion is positively charged to some extent, the emitted secondaryelectrons are pulled by the potential of the floating electrode. Thisreduces the efficiency with which the secondary electrons are acquiredby the secondary electron detector, resulting in a reduction in thesecondary electron signal luminance.

On the other hand, electric charges are discharged through the probefrom the wiring regions 106 to 108 with which the probe is electricallyconnected, so that there is no reduction in luminance in the secondaryelectron signal from these regions. Thus, a wire breakage portion 109can be identified based on the difference in secondary electronluminance before and after the broken connection plug 105.

If any subsequent breakage portions are to be identified, the probe 802is brought into contact with the metal wiring 107 located downstream ofthe above breakage portion according to the same flow. This way, asubsequent wire breakage portion 110 can be identified based on thedifference in secondary electron luminance. In this case, by applying avoltage between the probes 801 and 802 and thereby detecting the currentflowing therebetween, the resistance of the wire breakage portion can bemeasured.

By arranging the system so that the probes 801, 802, 803 and 804 can beswitched by the probe electric control apparatus 13 for each specificrole, such as the measurement of current or application of voltage, anydesired type of measurement can be conducted by any of the probes nomatter which electrode a particular probe is in contact with. Thisarrangement allows greater freedom of movement for the probes than isthe case when assigning a specific role, such as measurement of current,application of voltage or grounding, to each of the probes beforehand,making diagnosis easier.

In place of a FIB, an electron beam optical system 129 that is under thecontrol of an electron beam control apparatus 120 can be used. FIG. 23shows an example of the sample diagnosis apparatus using the electronbeam optical system 129. A sample 4 to be diagnosed, such as asemiconductor chip or wafer, is mounted on a movable sample base 5. Thesample is positioned for diagnosis by a sample base control apparatus 6by which the position of the sample base 5 is controlled. Four probes121, 122, 123 and 124 (although in the drawing the probes 122, 123 and124 are not shown to be connected to the probe electric controlapparatus 13, in fact they are) for supplying voltage to the sample 4and measuring the resistance, current or the like of the sample, underthe control of the probe electric control apparatus 13, are driven byprobe driving apparatus 125, 126, 127 and 128 (although in the drawingthe apparatus 126, 127 and 128 are not shown to be connected to theprobe control apparatus 9, in fact they are), under the control of theprobe control apparatus 9.

The sample 4 is irradiated with an electron beam emitted by an electronsource 1201 via an electron beam optical system 129 under the control ofthe electron beam control apparatus 120. The electron beam opticalsystem 129 comprises a beam limiting aperture 1202 for limiting theelectron beam emitted by the electron source 1201 to a predeterminedsize, a focusing lens 1203 for focusing the electron beam, and adeflector 1204 for deflecting the beam to a predetermined position onthe sample. Secondary electrons generated when the sample or probe isirradiated with the electron beam 130 from the electron beam opticalsystem 129 are detected by the secondary electron detector 10. Theoutput of the detector is fed to the display apparatus 12 as a luminancesignal in synchronism with the scan signal applied to the deflector1204. As a result, an image of the sample surface and images of theprobes 121, 122, 123 and 124 are displayed on the display apparatus 12.During this process, the probe control apparatus 9 is controlled by thesecondary electron information analyzing apparatus 11 identifyingspecific information in the secondary electron information. The electronbeam control apparatus 120, probe electric control apparatus 13, probecontrol apparatus 9, secondary electron information analyzing apparatus11, sample base control apparatus 6, and display apparatus 12 arecontrolled by the calculation processing unit 16. The calculationprocessing unit 16 may be realized in a personal computer or aworkstation comprising the electron beam control apparatus 120, probeelectric control apparatus 13, probe control apparatus 9, secondaryelectron information analyzing apparatus 11, and sample base controlapparatus 6. The sample image and the probe image may also be observedby detecting, with a reflected electron detector, electrons reflected bythe sample or probe and feeding a reflected electron detection signal tothe display apparatus 12.

However, as opposed to that which is the case with FIB irradiation,since both the primary electron beam 130 irradiated onto the sample andthe emitted secondary electrons are negatively charged, the chargedstate on the sample surface varies depending on the secondary electronemission efficiency, which is the average number of secondary electronsemitted per incident electron. Namely, when the secondary electronemission efficiency is smaller than 1, the sample surface is negativelycharged, while when it is larger than 1, the sample surface ispositively charged. For this reason, in order to identify the wirebreakage portion based on the state of charging as with the FIB samplediagnosis apparatus, the irradiation must be performed under conditionswhere the secondary electron emission efficiency has a value other than1.

The apparatus according to this example has the advantage that, sincethe irradiation beam 130 for observation is made up of electrons, thesample is not damaged even if it is irradiated for a longtime, incontrast to that which is the case with FIB. Thus, the apparatus isuseful when the probes 121, 122, 123, and 124 are to be contacted to amicroscopic region, such as a single electron transistor, with highaccuracy by the probe driving apparatus 125, 126, 127 and 128.

Embodiment 5

Referring to FIGS. 24 and 25, a probe control technique in which theprobe tip coordinates are recorded by preliminary contact of the probewill be described. The overall configuration of the apparatus is similarto the one shown in FIG. 1, so FIGS. 24 and 25 show only those portionsrelated to the probe driving apparatus 8.

FIG. 24 shows the height relationship between the sample 4 and the probe7 as seen from a direction parallel to the sample surface. Numeral 141designates a point-of-origin sensor indicating the position of the pointof origin (z=0) of the probe driving apparatus. In the state as shown inFIG. 24, while the probe driving apparatus 8 possesses probe-positioncoordinates information z along direction z as measured by a heightsensor 2500, it does not know the relationship between this informationz and the distance h between the probe tip and sample. In order toclarify the relationship between z and h, the probe 7 is brought intocontact with the sample 4 in advance, as shown in FIG. 25, before theprobe is actually used for the removal of a removed sample or iscontacted with a measuring electrode. This contact is confirmed bydetecting a change in secondary electron signal luminance, as describedabove or, if a conduction path is available, by detecting a contactcurrent. The z coordinate z0 of the probe driving apparatus upon theprobe 7 contacting the sample 4 is recorded by a probe referencecoordinates recording apparatus 2501.

Once this confirmation is made, when the probe z-coordinate is z, theheight h of the probe can be known at all times by a probe heightcalculator 2502 according to the following equation:h=z 0−zIn the present case, the probe 7 approaches the surface of the sample 4in a positive direction along the z-axis. Because the probe height canbe known, the probe can be brought into contact with the sampleaccurately in a short time without causing damage to the sample orprobe. For example, when the probe is actually used in the samplepreparation or diagnosis apparatus described in the above embodimentsfor removing a sample or contacting with a measuring electrode, theprobe 7 can approach the sample surface at a high speed up to such z(=z0−10 μm) that h=10 μm and thereafter, the approach speed can beswitched to a slower speed. In this case, however, since the probe 7 iscontrolled in an open-loop system which includes mechanical errors suchas backrush, a leeway must be provided in the z-axis tolerance range forthose errors. This embodiment is particularly suitable for a samplediagnosis apparatus in which the same probe is contacted a number oftimes.

INDUSTRIAL APPLICABILITY

The present invention enables the probe to be driven automaticallywithout causing damage to the probe or sample. The invention thereforeallows the operator to prepare a sample or electrically diagnose adevice sample in an efficient manner while putting less of a burden onthe operator.

1. A probe apparatus comprising: a sample base to mount a sample; acharged particle beam optical system to irradiate a charged particlebeam to the sample; a detector to detect secondary electrons orreflected electrons which generate from the sample; a probe to contactwith the sample surface; a probe control apparatus to control movementof the probe; an analyzing apparatus to determine a height between a tipof the probe and the sample surface, and to analyze a signal from thedetector; and a display apparatus to display an image of the signal,wherein the display apparatus displays the information of the heightbetween the tip of the probe and the sample surface based on theanalysis result.
 2. A probe apparatus according to claim 1, wherein theanalyzing apparatus determines a relation of the height between the tipof the probe and the sample surface based on a change in luminance ofthe image.
 3. A probe apparatus according to claim 1, wherein thedisplay apparatus displays a numerical value of the height which isdetermined by the analyzing apparatus.
 4. A probe apparatus according toclaim 1, wherein the analyzing apparatus calculates a probe drive speedaccording to the height.
 5. A probe apparatus according to claim 4,further comprising: a probe control apparatus to control a movement ofthe probe based on the calculation result.
 6. A probe apparatusaccording to claim 4, further comprising: a probe operating apparatuswhich makes the probe apparatus approach the sample manually based onthe calculation result.
 7. A probe apparatus according to claim 1,further comprising: a probe control apparatus to control a movement ofthe probe based on the information of the height.
 8. A probe apparatusaccording to claim 6, further comprising: an input device to operate theprobe.
 9. A probe apparatus according to claim 8, wherein the inputdevice includes a push button, joystick or mouse.
 10. A probe apparatusaccording to claim 7, further comprising: an input device to operate theprobe.
 11. A probe apparatus according to claim 10, wherein the inputdevice includes a push button, joystick or mouse.
 12. A probe apparatusaccording to claim 1, further comprising: a buzzer or an indicator tocaution when the height approach a preset value.
 13. A probe apparatusaccording to claim 5, wherein the probe control apparatus makes theprobe drive speed slow down when the height approaches a predeterminedvalue.
 14. A probe apparatus according to claim 4, further comprising; aprobe control apparatus to control a movement of the probe; a probeoperating apparatus which makes the probe apparatus the sample manually;and a changeover switch to select the analyzing apparatus or the probeoperating apparatus based on the calculation result.
 15. A probeapparatus according to claim 1, further comprising: a probe controlapparatus to control a movement of the probe; a probe operatingapparatus which makes the probe approach the sample manually; and achangeover switch to select the analyzing apparatus or the probeoperating apparatus based on the information of the height.
 16. A probeapparatus comprising: a sample base to mount a sample; a chargedparticle beam optical system to irradiate a charged particle beam to thesample; a detector to detect secondary electrons or reflected electronswhich generate from the sample; a probe to contact with the samplesurface; a probe control apparatus to control movement of the probe; ananalyzing apparatus to determine a distance between the probe and thesample surface, and to analyze signal from the detector; and a displayapparatus to display an image of the signal, wherein the displayapparatus displays the information of the distance between the probe andthe sample surface based on the analysis result.